Process for making fluorspar briquettes



July 17, 1962 Filed Oct. 6, 1959 Fluorspor Fines Add 0.1 to 0.3% Sulfonoied Lignin Binder Shape Muss Into Briqueire Dry Shaped Moss Fire Shaped Mass at Progressiveiy Increasing Temperuiure Ruie of about 2- 8F per min.

End Product is a Unitary, Shnped Hard ,Porous Dense,

Briquetie Consisting of Fluorspur Fines wann Maw ATTORNEYS 3,044,140 PROCESS FOR MAKING FLUGRSPAR BRIQUETTES James R. Coxey, Reading, Pa, assignor to Glen Gery Shale Brick (Iorporation, Reading, Pin, a corporation of Pennsylvania Filed Oct. 6, 1959, Ser. No. 844,618 Claims. (31. 25-157) This invention relates to a process for making fluorspar briquettes and, in particular, to a process for making fluorspar briquettes from fluorspar fines.

Fluorspar is the commercial name for the mineral fluorite, which is chemically calcium fluoride (CaF and which occurs in the United States and certain foreign countries, including Italy, Newfoundland, Sardinia, Mexico, and Spain. The natural product from the mining operation, whether by the open pit method or the deep shaft method, are aggregates of various sizes, together with a quantity of finely divided, powdery material of small mesh size which is termed fluorspar fines. Because of the handling involved in transportation of the aggregates from the mines to. the ultimate user, a progressively larger quantity of fines is created at each stage of handling, almost all of which is non-usable and is considered waste.

Fluorspar is at present the only commercial source of fluorine, and it is necessary to the production of aluminum, steel, and hydrofluoric acid as well as in the production of products such as Freon gas, high octane gasoline, glass, and enamelware. Fluorspar is absolutely essential in the melting operation of ferrous metallurgical practice, which includes the manufacture of steel by the open-hearth process, the electric arc process, by cupola practice, and by the several other known forms of steel melting. Approximately five pounds of fluorspar are presently required to flux each ton of steel, and this amount is added to the molten steel batch in its aggregate form.

Because of the excess amount of finely divided powder or fines produced each time fluorspar is handled, it is diflicult, time-consuming, and costly to measure out the exact amount of fluorspar required'per each batch of molten steel. Furthermore, the fines which are present with the fluorspar aggregates cannot be utilized in the charging of a steel melting furnace because of their low specific gravity, due to their finely divided condition. Instead of sinking into the molten charge, they are blown out through the flue and are lost. These charging losses, when added to the storage and handling losses due to the creation of fines, have been an added cost factor in the steel melting process and have precluded the commercial use of the one grade of fluorspar that is greatly to be preferred by virtue of its superior chemistry over presently used fluorspar material.

There are several grade classifications of iluorspar. The one presently in use in metallurgical practice is defined as metallurgical grade and consists of approximately 72.5% effective units of calcium fluoride. An effective unit of fluorspar is defined as the calcium fluoride content minus 2 /2 times the silica content. Silica 'is an impurity in fluorspar which drastically degrades its much as 10% silica. Since the effectiveness of fluorspar as a flux is-a direct function of the effective units of calcium fluoride that are available to react as a flux, then it is obvious that acid grade is much more effective in its intended function than is metallurgical grade.

However, inasmuch as acid grade fluorspar is much more expensive than metallurgical grade, the losses due to the occurrence'of fines before the fluorspar is used has heretofore precluded its use in metallurgical practice. Hence, the use of acid grade =fluorspar has been confined almost exclusively as a raw material source in the manufacture of hydrofluoric acid and, in turn, a source for the production of fluorine.

Attempts have been made in the past to commercially utilize the fluorspar fines by forming agglomerates, such as pellets and the like therefrom, but the binding materials which have been used in such processes form an integral part of "the shaped, unified mass and degrade ,the effectiveness of the fluorspar material as a flux. Further more, they may result in impurities in the finished steel product. Thus these formed units have not been satisfactory for use in, the commercial steelmaking processes.

If the fluorspar fines, per se, with or without added water, are compressed into molds or dies, and heated to the necessary high temperature :to form a briquette, the

formed product adheres tenaciously to the mold or die and cannot be removed therefrom. If water is added to the fluorspar fines, per se, and the mixture is shaped and dried without the use of molds or dies, it immediately disintegrates upon handling.

Accordingly, it is an object of this invention to utilize the finely divided, powdery particles or fines which are formed during the handling of fiuorspar aggregates or which are intentionally produced as a raw material source shaped, unitary masses. When the fines have been intentionally produced by conventional mineral concentration methods for use as a raw material source for the manufacture of hydrofluoric acid or other uses, the fines so produced are known as filter-cake.

It is another object of this invention to provide a process for making a fluorspar briquette consisting essentially of fluorspar fines wherein the fines are consolidated into a solid, interlocked, unitary mass.

It is another object of this invention to provide a process for producing a fluorspar briquette of predetermined shape and weight consisting essentially of fluorspar fines which are consolidated and interlocked to each other at adjoining surfaces in such a manner that they can withstand the handling involved in transportation without dissociation into useless, finely divided powder or fines.

In attaining the objects of this invention one feature resides in mixing the fluorspar fines with a binder material, which material remains in the mixture during the early stages of the process and permits shaping of the fines in a mold or die, and which material assists in the retention of the molded shape while drying, but which binder material is removed during the subsequent step of firing the shaped mass, and the resultingproduct consists essentiallyof a hard, porous mass of'consolidated, interlocked fluor'spar fines bonded at adjoining surfaces to each other, and which mass does not dissociate into useless, fine powder or fines when handled.

Other objects, features, and advantages of this invention will be more apparent from the following disclosure. 7 Basically, the process for the manufacture of fluorspar bricks comprises the utilization of fluorspar fines, such as the acid grade fines, by forming them into shaped masses of predetermined Weight, which can be easily handled, without again dissociating into fines.

Basic to the invention is the discovery that the fluorspar fines may be admixed with a binder having the characteristics of assisting in the formation of a shaped mass of Patented July 17, 1962 I into a unitary, hard, dense mass, not unlike abrick,

wherein the particles tightly adhere to each other and do not dissociate into fines upon further handling. Furthermore, after performing the above functions, the binder material has the characteristic of being removable from the shaped mass during the firing step so that "no binder material remains in'the final product, which product consists essentially of a. porous mass of tightly bound fiuorspar fines. Thus, the binder material is present only in the early phases of'the process and performs the function of holding the fines together until such time that the temperature in the kiln causes the fines to bond from .binder as determined by chemical and spectrographic means so that it is apparent that the sole function of the 1 sulfonated lignin binder is to hold the fluorspar'fines to to each other while the binder is. removed, such as'by' V volatilization, from the mass.

Included among the binders having the required char acteristicsare the products known broadly as the sul- "fonated l-ignins or ligno-sulfonates which are principally obtained from the waste sulfite liquors resulting from the sulfite process of pulping ligno-cellulose materials, including the base metal ligno-su-lfonatesl such as sodium, potassium, ammonium, lithium, and the like.

The principal constituent of sulfite waste liquor is l-ignosulfonic acid, which is usually present in the form of a salt corresponding to the particular base material used in the sulfite pulping process, The most common bases used include sodium, potassium, lithium, ammonium, etc.

As a natural occurrence during the pulping process, a number of phenolic acids are found in the waste sulfite liquor and alkali treatment of the liquor, such as with sodium hydroxide, results in the formation of alkali metal salts of the mixed phenolic acids of the waste sulfite liquor. These alkali metal salts have been found to be particularly suitableas binders for the process of the invention. A sodium salt of mixed phenolic'acids obtained bythe NaOH treatment of Waste sulfite liquor is sold by the West Virginia' Pulp and Paper Co. under the trademark Indulin C-Special." phenolic derivatives of, waste sulfite liquor such as are obtained by the reaction of phenol and other phenolic gether until such time that the temperature causes the iluorspar fines together.

The following example is merely illustrative of the invention and is not to be considered limiting the scope thereof in any manner.

Example I l A given quantity of acid grade fines of a size such that 100% pass through a 100 mesh screen and 60% pass through a 325 mesh screen and containing 9% moisture was mixed with 0.3% by weight of a sodium salt of mixed phenolic acids obtained by alkali treatment (NEZOH) of waste sulfite liquor (Indulin C-Special) until ahomogeneous mixture was obtained. The mix was transferred to a mechanical ramming machine and shaped in the cform. of a :brick which had a predetermined weight of about five pounds. The 'bricks that were formed were dried in a dryer and then placed in a kiln and fired at the rate of 6 F. per minute'to a final temperature of 1750 F. after which they'were removed and cooled to room temperature.

v The firing process totally removed all traces of the binder as determined by chemical and spectrographic Also suitable are the compounds with the waste sulfite liquor in accordance with known processes.

TO -agglomerate acid grade'fluorspar fines, a known quantity thereof is mixed with from about 0.1 to about 0.3% by weight-of a snlfonated lignin, such as an alkali metal ligno-sulfonate, or the sodium salt of mixed phenolic acids obtained by alkali treatment of waste sulfite liquor, more or less of the lignin being required to counteract the varying degree of moisture that is native to the fiuorspar fines, usually from 7 to 12% by weight. Best results are obtained when the moisture content is from The mixing of a small quantity of the dry binder or an aqueous suspension of the'binder with a large quantity of fines can best be conducted in a meohanical coun- 'terflow mixer and a mixing time of about ten minutes is required to form a homogeneous mixture. The time will, of course, vary with the particular mixing apparatus used.

When an aqueous suspension of binder is mixed with the fluorspar fines, care must be taken that the total amount of'moisture inthe mixture does not exceed 12% by weight ofthe fluorspar. It is preferred to use a binder which is soluble in the small amount of moisture available in the fluorspar.

The mixture is then transferred to a mechanical or hydraulic ramming machine where the plungers force the prepared mixture into dies of predetermined size, the resultant shape from which has a predetermined weight.

analysis,

An analysisof a sample brick showed that it had the following composition.

R 0 is aformu-la used by the art to indicate a mixture of certain metal oxides such as aluminum, titanium and iron oxides. l

It been found that best results are obtained when the kiln is fired at the rate of about 2 F. to 8 F. per

minute to a final temperature of 1650 F. to 1850 F.

Whilea rate of less than 2 F. per minute may be utilized,

it unnecessarily prolongs the firing time cost of the final product.

Specifically acid grade filter-cake (100% through 100 mesh and at -least'60% through 325 mesh) is preferred tor the process of forming a brick-like, brick-shape, and brick-weight mass that can be charged as a flux in the steel-melting process to replace the present practice of charging irregular sizes, shapes, and weights-of lumpy fluorspar. By manufacturing these fiuorspar briquettes and adds to the in units Weighing approximately fivepounds' each, one

knowing the Weight of the molten steel charge in the furnace can easily add the exact number of fluorspar bri-' quettes necessary to accomplish the required job of fluxing, since approximately one fluorspar briquette is required for each ton of steel. While the melting point, 2480 Fl, of the'fiuorspar briquette formed by the process of the invention is the. same as ordinary lump fluorspar, the latter, when subjected to a temperature of about 1200 .F. to 1400 F. disintegrates,

, due to the relieving otthe stresses in its structure, before reaching its melting point. t-ion, on the other hand, will withstand much higher tem- The b-riquette of the invenperatures and will dissolve in a steel melt before disintegrating.

By using the shaped units formed by the process of this invention, it will no longer be necessary for a steel mill to stockpile large amounts of fiuorspar in enclosed facilities and sustain the substantial loss of the fiuorspar which distintegrates into unusable fines. Instead, it is now possible to utilize all of the fiuorspar which is purchased in the shape of bricks and made in accordance with this invention. Furthermore, for the first time, it will be more economical to use the acid grade fiuorspar for metallurgical purposes such as the various processes for melting steel because of the presence of more effective units of calcium fluoride, per unit of weight.

Having fully described the invention, what is claimed 1. The process for forming a unitary, shaped, fiuorspar briquette comprising shaping a mixture consisting essentially of acid grade fiuorspar fines and from about 0.1 to about 0.3% by weight of a sulfonated lignin binder therefor, the total moisture content of said mixture being from about 7 to 12% by weight, drying the shaped mass, and firing the dried mass at a rate of about 2 to 8 F. per minute to a temperature sufiicient to remove said binder from said shaped mass and consolidate said fines into a unitary, porous, hard, dense mass.

2. The process as defined in claim 1 wherein said mixture has a total moisture content of from 9 to 9.5% by weight.

3. The process for forming fiuorspar briquettes as defined in claim 1 wherein said acid grade fiuorspar fines have a size such that 100 percent pass through a 100 mesh screen and at least 60 percent pass through a 325 mesh screen.

4. The process as defined in claim 1 wherein said shaped mass is dried to a moisture content of less than 0.2% by weight.

5. The process as defined in claim 1 wherein said sulfonated lignin binder is an alkali metal ligno-sulfonate.

6. The process as defined in claim 5 wherein said alkali metal ligno-sulfonate is sodium ligno-sulfonate.

7. The process for forming fiuorspar briquettes comprising shaping a mixture consisting essentially of acid grade fiuorspar fines and from about 0.1 to about 0.3% by weight of a binder which is an alkali metal salt of mixed phenolic acids of waste sulfite liquor, said mixture having a total moisture content of from about 7 to 12% by weight, drying the shaped mass, and firing the dried mass at a rate of about 2to 8 F. per minute to a temperature sufiicient to remove said binder from said shaped mass and consolidate said fines into a unitary, porous, hard, dense mass.

8. The process as defined in claim 7 wherein said alkali metal salt is a sodium salt of mixed phenolic acids of waste sulfite liquor.

9. The process for forming fiuorspar briquettes comprising shaping a mixture consisting essentially of acid grade fiuorspar fines and from 0.1 to 0.3% by Weight of a sulfonated lignin binder, said mixture having a total moisture content of [from about 7 to 12% by Weight, drying the shaped mass, and firing said dried mass at a rate of about 2 to 8 F. per minute to a temperature of from about 1650 to 1850 F. to remove said binder from said shaped mass and consolidate said fines into a unitary, porous, hard, dense mass.

10. The process for forming fiuorspar briquettes comprising shaping a homogeneous mixture consisting essentially of acid grade fiuorspar fines of a size such that 100 percent pass through a 100 mesh screen and at least percent pass through a 325 mesh screen, and 0.3% of a binder which is the sodium salt of mixed phenolic acids of waste sulfite liquor, said mixture having a total moisture content of about 9% by weight, drying the shaped mass, and firing the dried mass at a rate of 6 F. per minute to a temperature of 1750 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,232,242 Jordan 'Feb. 18, 1941 2,549,822 Koonce Apr. 24, 1951 2,580,708 Wallace Jan. 1, 1952 2,833,659 Bauer t May 6, 1958 OTHER REFERENCES -Lewis: Paper Trade Journal, vol. 127, No. 2 (July 8, 1948), pages 5l-52 (Tappi Section, pages 308309). 

1. THE PROCESS FOR FORMING A UNITARY, SHAPED, FLUORSPAR 